Seam weld shell element model for thin walled structure FE fatigue design

Abstract

In automotive industry, the FE fatigue analysis of mechanical structures made of steel thin walled parts and seam welded assemblies uses a dedicated technique based on shell element modelling for components and on 1D rigid elements for welds. This method has been validated with several intensive fatigue test campaigns using gas metal arc welded samples with different assemblies, for both bending and torsional loads. The fatigue results are relative to crack initiation at the weld toe with bending normal stress or with longitudinal shear stress for several load ratios. The purpose of the current work is the transposition of the initial method to another FE welded model. In a recent IIW guideline for the assessment of weld root fatigue, a shell element weld model has been proposed for seam weld fatigue assessment in case of weld root crack initiation. The idea is to analyse the possible extension of this FEA weld element model for weld toe fatigue analysis and several comparisons of stress results are detailed and discussed. Different fatigue criteria are used to verify the correlation with the fatigue test results. First, the approach is based on maximum shear stress, then structural stress is calculated and results are compared to IIW S/N curves.

Finite Element Analysis of Joints, Comparison of Results with the Component Method According to EN 1993‐1‐8:2005

“…Welds are modelled by direct connection between plates to be welded by means of forcedeformation constraints, also known as Multi Point Constraints. The technique of modelling welds by rigid connections was suggested by Fayard and Bignonnet (1996) [6], and can also be found in various scientific papers such as [7], [8], [9] or [10].…”

Numerical Prediction of the Fatigue Life of Complex Riveted Structures

“…is very mesh sensitive, which can lead to inaccurate fatigue life predictions. For riveted joints, a simplified version of the model exists [20][21][22][23][24][25]. According to this model (1), ( 2) and (3) become the following for sheet metal failure:…”

Numerical prediction of the fatigue life of complex riveted structures

“…The structural stress method has also been used successfully to assess the fatigue life of spot-welded components [14]. This technique can also be used with some modification to model riveted joints [16][17][18][19][20].…”